document.write( "Question 37779: How do use a half-angle formula to find the exact value of sin 7pie/8 ? \n" ); document.write( "
Algebra.Com's Answer #23408 by fractalier(6550)\"\" \"About 
You can put this solution on YOUR website!
The half angle formula for sin(theta) is
\n" ); document.write( "sin(theta/2) = ± sqrt[(1 - cos(theta)) / 2]
\n" ); document.write( "If we know cos(7pi/4) = sqrt(2) / 2, we just plug it in, so we get
\n" ); document.write( "sin(7pi/8) = ± sqrt[(1 - sqrt(2)/2) / 2]
\n" ); document.write( "(It is clumsy to do trig this way, ya know...) \n" ); document.write( "
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